This invention relates to organopolysiloxane emulsions. More particularly this invention relates to 1,2-diol functional organopolysiloxane emulsions. This invention also relates to 1,2-diol functional organopolysiloxane emulsions which can be prepared by a variety of methods.
Emulsions are mixtures of at least two components which are substantially immiscible in each other, and a surfactant which stabilizes the particles of one component against coalescence when dispersed in the other component. A microscopic view of aqueous emulsions reveals two phases, an oil phase and a water phase. The emulsion can be characterized as an oil-in-water emulsion or a water-in-oil emulsion. The chief distinction between the two being which component, the oil or water phase, comprises the continuous portion of the emulsion. The noncontinuous phase is in the form of droplets in the other phase.
Polysiloxane emulsions may be categorized by the size of the polysiloxane particles and the appearance of the emulsion. Typically three categories of silicone emulsions are recognized in the art: standard emulsions, fine emulsions, and microemulsions. The term "emulsion" as used herein encompasses the three individual types of silicone emulsions.
Silicone standard emulsions are characterized by a large particle size (typically greater than 300 nanometers) and appear to the human eye to be opaque (impenetrable to light). Silicone standard emulsions are most commonly identified as those having an intense white appearance. Silicone fine emulsions are characterized by a smaller particle size, from 300 to 140 nanometers, and are identified as those compositions which visually may be opaque to very slightly translucent (transmitting light but with distortion). Silicone microemulsions are characterized as those having a particle size of less than 140 nanometers and visually appear translucent to transparent (transmitting light without distortion).
Out of the three types of silicone emulsions, fine emulsions and microemulsions are the most desired due to their smaller particle size and higher stability. Microemulsions are further desired due to their translucent to transparent appearance.
Methods for making emulsions of polysiloxanes in water are well known in the art. The methods are generally classified in two categories: mechanical means and emulsion polymerization. Mechanical means usually entail taking the polysiloxane and using mechanical means such as homogenizers or vigorous agitation to emulsify the siloxanes in water. Typically a surfactant is added to the polysiloxane or water to aid the emulsification process.
Emulsion polymerization typically entails combining a reactive silicone oligomer, surfactant, polymerization catalyst and water. The mixture is stirred or emulsified and the silicone oligomers are allowed to polymerize until a standard emulsion, fine emulsion or microemulsion of polysiloxane is formed. Typically alkoxysilanes, which result in the formation of microemulsions, or cyclosiloxanes, which result in the formation of fine and standard emulsions are used as the reactive monomers and oligomers.
Typical problems encountered with emulsion polymerization of cyclosiloxanes include the presence of an unemulsified silicone oil layer or very large (visible to the human eye) silicone oil droplets in the final emulsion produced. Using methods known in the art, complete elimination of the silicone oil layer is not achieved unless the cyclosiloxane is pre-emulsified using mechanical means prior to polymerization. Mechanical pre-emulsification of the cyclosiloxanes in water prior to emulsion polymerization is a common, well known practice to those skilled in the art.
Silicone emulsions produced by emulsion polymerization have been disclosed in the art. For example U.S. Pat. No. 2,891,920 to Hyde et al. teaches an emulsion polymerization method where the siloxane oligomer, emulsifying agent (cationic, anionic or nonionic surfactant), catalyst and water are all blended together (in various orders) to form an emulsion and then allowed to react at room temperature or greater. It appears that it is possible to produce only standard and possibly fine emulsions by this method.
U.S. Pat. No. 3,294,725 to Findlay et al. teaches an emulsion polymerization method wherein a mechanically produced pre-emulsion is made of the siloxane in the presence of the catalyst. Heat is then applied to this emulsion and the siloxanes react to form the polysiloxane emulsion. Various sulfonic acids and their salts are taught as the catalysts for the polymerization. The catalysts also act as the emulsifying agent thereby eliminating the need for additional materials. The examples provided in the Findlay patent show that when cyclosiloxanes are employed as the starting material, less than 90% of the starting cyclosiloxanes are consumed after several days of reacting. It appears that only standard and fine emulsions can be produced by this method. The resulting emulsions however have a narrow distribution of particle sizes.
A method for preparing colloidal suspensions of silsesquioxanes is taught in U.S. Pat. No. 3,433,780 to Cekada et al. These colloidal suspensions have an extremely small particle size (10 nanometers to 100 nanometers) and in most cases contain less than 25% by weight of the silsesquioxane. The method comprises combining the water and catalyst, heating the water solution (optional) and rapidly or slowly adding a trialkoxysilane to the water solution. When rapid addition is employed the suspension can contain up to 10% by weight of the silsesquioxane. Silsesquioxane are materials which contain 3 Si--O bonds per molecule.
Several papers have been published in China on studies of silicone emulsion polymerization using cationic surfactants and in some experiments, additionally using nonionic surfactants. A paper published by Northwestern University of Light Industry, China, Xibei Qingongye Xueyuan Xuebao, No. 4, pp. 5-10, December 1987, discusses the improved stability of emulsion produced using a nonionic surfactant and an anionic surfactant.
Additionally, two papers, Institute of Chemistry, Academia Sinica, Beijing, China, Polymer Communications, No. 4, August 1982, pp. 266-270 and pp. 310-313, report on the mechanism of cationic emulsion polymerization and the effect of temperature on cationic emulsion polymerization, respectively.
Gravier et al. in U.S. Pat. No. 4,999,398 discloses a clear stable, stable, aqueous microemulsion of polydiorganosiloxane produced by a method which comprises sequentially adding a precursor emulsion comprised of a cyclopolydiorganosiloxane, surfactant, and water, to a polymerization medium comprised of water and an effective amount of a polymerization catalyst while mixing. During this process the cyclosiloxane monomer particles are consumed and new much smaller polysiloxane polymers particles are formed.
Japanese Patent Application Publication No. 04-327,273 (327,273/1992) discloses a fiber treatment agent which is an organopolysiloxane which contains an aminoalkyl group and a triglycerol group, and further discloses that this organopolysiloxane can be dispersed in water with a surfactant to form an emulsion.
European Patent No. 0459500 discloses a method for making oil free polysiloxane standard emulsions, fine emulsions, or microemulsions using emulsion polymerization, the method comprising reacting a cyclosiloxane in the presence of a catalyst, ionic surfactant, and nonionic surfactant. EP'500 further discloses that emulsions containing siloxane copolymers can also be produced using this method. This patent teaches a method for controlling particle size produced during emulsion polymerization.
The methods known in the art using emulsion polymerization however do not disclose the use of at least one epoxy functional silane to produce an emulsion of siloxane polymer containing pendant organic 1,2-diol groups. Further, the methods known in the art do not disclose the use of such an emulsion of 1,2-diol functional polysiloxane as a fiber treatment agent to provide improved sensory feel and which retains or provides hydrophilicity of the treated substrate.